The Fish That Walks on Stilts

One of the denizens of the deep is the 30cm long tripod fish, Bathypterois grallator. This unusual fish is typically found anywhere between 1-5km deep in the Atlantic, eastern Pacific, and western Indian, although future exploration wil likely reveal that is global. First described over a century ago in 1886, the common name comes from the modified pelvic and lower caudal fins that are elongated. Although rigid on the seafloor, the video above demonstrates these fins can be quite flexible while swimming. The scientific name comes from the Greek bathus meaning deep, Greek pterois meaning feathery referring to the spines of a fish, and the Latin grallator, one who walks on stilts.

The video also shows that on these modified finds the tripod fish can stand on the seafloor. The tripod allows the fish actually to place itself up off the bottom. The need for this stems from the fact that currents centimeters near the bottom are slow to nonexistent. This layer called the benthic boundary layer is not the ideal place to wait for food. This is the same reason why you often see filter feeding seastars, basketstars, and brittlestar, among many other organisms, climb high on corals and sponges.

It is hypothesized that the fish uses the elongated pectoral fins, seen in the below video extending above the head, to detect small crustaceans coming in as the fish faces into the current. These elongated pectoral fins also are thought to direct the crustaceans toward the mouth.

Another interesting tidbit about this species…its a simultaneous hermaphrodite.

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, created to facilitate research to address fundamental questions in evolutionary science. He has conducted deep-sea research for 11 years and published over 40 papers in the area. He has participated in dozens of expeditions taking him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses mainly on marine systems and particularly the biology of body size, biodiversity, and energy flow. He focuses often on deep-sea systems as a natural test of the consequences of energy limitation on biological systems. He is the author and chief editor of Deep-Sea News, a popular deep-sea themed blog, rated the number one ocean blog on the web and winner of numerous awards. Craig’s popular writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.